1. Field of the Inventions
The present inventions generally relate to engine control systems, and more specifically, to a shift cutout control system to facilitate interception of the power transmission, i.e. shift cutout, in an internal combustion engine having ignition cutout control for deactivating certain cylinder(s).
2. Description of the Related Art
An outboard motor of a watercraft uses power transmitted from an internal combustion engine to drive a propeller. This power is controlled by shifting a control lever among a forward position (causing propeller rotation in forward direction), a neutral position, and a reverse position (causing propeller rotation in an opposite direction), which shifting actuates a dog clutch. In the case of hard deceleration during the high-speed operation of the engine, shift cutout cannot be performed by merely lowering the throttle or dropping the engine rpm. A shift cutout control is implemented in such situations to reduce the torque of the engine by suspending the ignition operation in certain cylinder(s).
One example of the conventional shift cutout control device, as shown in FIGS. 6 and 7, has a shift cutout switch in the shifting force transmission path. The torque of the internal combustion engine is reduced by cutting out the ignition in the engine once the shift cutout switch detects a shifting force that exceeds the predetermined level. See e.g. Japanese Patent Document No. JP-A-Hei 2-216391.
The example shown in FIGS. 6 and 7 uses a mechanical remote control device for controlling shift cutout. As shown, a movable bracket 54 has a guide rail 53 that is supported swingably by a bearing section 52. The bearing section 52 is provided on a fixed bracket 51 that is fastened in the area around the internal combustion engine 50. A roller 55 is assembled into the guide rail 53 such that it rolls in the guide rail 53. A pin 56 is inserted through a center of the roller 55. A terminal of a remote control cable 57 is joined to one end of the pin 56, and an end of the connecting lever 58 is joined to the other end of the pin 56. The other end of the connecting lever 58 is joined to a free end of a lever 60 that is connected to a shift rod 59. The shift rod 59 is used for operating the dog clutch (not shown) such that a propeller rotation can be switched among neutral, forward, and reverse.
The fixed bracket 51 has a first stopper 61 for blocking the movable bracket 54 from clockwise rotation, as in the FIG. 6. In addition, a torsion spring 63 is interposed between the fixed bracket 51 and the movable bracket 54 around a support shaft 62. A biasing force is imposed by the torsion spring 63, causing the movable bracket 54 to be constantly biased against the first stopper 61.
The fixed bracket 51 has a shift cutout switch 64, and the movable bracket 54 has a pressing part 65. The pressing part 65 closes the contact point of the shift cutout switch 64 when the movable bracket 54, resisting the force of the torsion spring 63, is rotated counterclockwise in FIG. 6 from a butting position against the first stopper 61. Also, the fixed bracket 51 has a second stopper 66 for blocking the counterclockwise rotation of the movable bracket 54 after the contact point of the shift cutout switch 64 is closed.
In conventional shift cutout control devices similar to that described above, the roller 55 is moved along the guide rail 53 by the shifting force exerted on the remote control cable when the control lever of the remote controller is rotated. The movement of the roller 55 results in corresponding movement of the connecting lever 58, which is joined to the roller 55. Then, the lever 60 joined to the connecting lever 58 makes a swinging motion to rotate the shift rod 59, which causes the shifting of the dog clutch. On the other hand, as the roller 55 is moved along the guide rail 53, the shifting force from the forward position to the neutral position (shifting force fF) or the shifting force from the reverse position to the neutral position (shifting force fR) imposes a given preset level of force (namely the shifting force necessary to shift back to neutral position from forward or reverse position). Then, the movable bracket 54 rotates counterclockwise to turn on the shift cutout switch by the pressing part 65. The turn-on signal of the shift cutout switch 64 is transferred to the ignition control circuit of the internal combustion engine 50. Receiving the turn-on signal, the ignition control circuit determines that the shift cutout switch 64 has sensed the occurrence of shifting force fF or fR exceeding the given level, and implements the ignition cutout in the internal combustion engine 50 to reduce its torque. The shift cutout operation is therefore facilitated in this manner.
In the case of shift cutout control systems of the conventional mechanical remote control devices described above, the shift cutout switch 64 is used to detect the conditions for initiating the shift cutout. Simply, the shift cutout switch 64 mechanically reads the shifting force transmitted to the remote control cable 57 through the rotating motion of the control lever. In such a system, the performance of the shift cutout control is dependent on the quality of the shift cutout switch 64, and the space for attaching the shift cutout switch 64 must be maintained on the internal combustion engine 50.